Crack Tip Strain Field and Its Propagation Characteristics in a Polymer Foam

Abstract

In recent years there has been an increasing interest in using foam composites as shipbuilding materials. A sandwich panel built of fiberglass face sheets and a foam core has strong rigidity and bending strength. It’s advantage for ship construction is obvious. Furthermore when a small amount of nanoparticles are added to the material, it tends to increase its stiffness and retards fire as well. In this paper we employ a unique micro/nano speckle technique to investigate the crack tip deformation field of two different polymer foams at a length scale that has never been studied before. The principle of the technique is described in [1]. Figure 1 shows the micrograph recorded by a scanning electron microscope of a crack propagating through a NEAT foam specimen under uniaxial tension. The void in front of the crack tip was kind of spontaneously generated as a result of the load. The main crack then tends to link itself towards the void as demonstrated in the sequence of pictures shown.